The finding, reported in the journal Neuron, provides the first scientific evidence to help explain why it is easier learn about something that you're interested in, than if you're bored stiff.

Importantly, it seems that the enhanced learning ability is not limited to the thing that excites your curiosity: the curious state enables you to better learn about unrelated things too, says study co-author Professor Charan Ranganath of the University of California, Davis.

"Our results suggest that when people are in a state of curiosity it induces a motivational state and that actually helps you suck in other information as well," he says.

The researchers say their findings could point to ways to enhance learning in the classroom and may help understand memory problems in elderly people.

The study looked at 19 university students aged between 18 and 31. The students were asked trivia questions. When they didn't know the answer, they were asked to rate how curious they were about the answer on a scale from 1 to 6.

The researchers then put each student into a scanner which could measure the activity of various brain regions using functional magnetic resonance imaging (fMRI).

While in the scanner, the students were asked only the questions that they were most or least curious about, in a random order.

They had to wait 10 seconds for the answer, during which time they were distracted by being shown a photo of a person's face, and asked how likely that person was to know the answer to the question.

Afterwards they were tested on their memory for the answers to the trivia questions. They were much better at recalling answers to questions they found interesting, than answers to questions they were not curious about.

The researchers also tested how well the students could remember the faces they had been shown.

Surprisingly, the students were more likely to remember the face of someone that they were shown while pondering a question that they were curious about.

"It turns out that the faces, so to speak, come along for the ride," says Ranganath.

Rewarding circuit

"What's interesting is that the brain areas that are ramping up while they wait for the trivia answer are in the circuit that is generally involved in processing reward," he adds.

These same areas will be activated if a person is offered a $20 note, or if they are shown a picture of food, he explains.

"But here they are not anticipating any money, they're not anticipating any food, but they are anticipating something they are motivated to learn and we see a ramp-up that's very similar."

Professor John Hodges of NEURA, who was not involved in the research, says it looks like a very good study.

"Like a lot of research, they've investigated and found something that one would believe to be intuitively correct, but it's never been shown before -- that if you're interested in a topic then you are more likely to retain and learn," says Hodges.

"They've shown that there is one brain system that's to do with arousal and curiosity and that has an influence on another brain system that is to do with memory and the two are interacting," he adds.

He says the results show that the level of curiosity regulates the nucleus accumbens, a brain area associated with arousal and addiction.

"The nucleus accumbens is implicated in drug addiction and in people who play video games." It's an important part of the brain's reward circuit, he explains.

The study shows the nucleus accumbens is also more active if you are curious and interested and that it, in turn, is influencing the areas of the brain to do with memory, he says.

Hodges says the work has been possible because brain imaging has improved dramatically and now changes in tiny structures like the nucleus accumbens can be seen.

"This work has obviously got implications for teachers and how to teach adolescents," he adds. "The key thing is to make things interesting and increase people's curiosity and then they learn naturally."